The American Cancer Society estimates that 62% of all cancers could be prevented altogether through lifestyle change. Indeed, two of every five premature deaths in the U.S. can be linked to unhealthy and ultimately modifiable behavioral choices. Despite good intentions, people's attempts at midlife lifestyle change often fail, paving the way to increased cancer risk and other costly and life-limiting chronic conditions. The overarching goal of the proposed research is to investigate the role of positive emotions in facilitating successful lifestyle change, defined as healthy behavioral decisions repeated daily, or near daily. An innovative upward spiral model of lifestyle change integrates multiple streams of research in basic behavioral and brain sciences to position positive emotions as key active ingredients that not only seed nonconscious motivational pulls toward a newly-adopted wellness behavior, but also reshape key biopsychosocial resources in ways that increase the subsequent positive emotion yield of that behavior, creating a self-sustaining dynamic system. Four tightly- controlled laboratory experiments test this new model by targeting three Specific Aims. These aims are: (1) to test whether and how positive emotions and physical pleasures differentially create nonconscious cognitive and affective processes that mediate behavioral decisions; (2) to identify biopsychosocial resources that moderate the link between a wellness behavior and its positive emotion yield, and in turn create nonconscious motives for that behavior; and (3) to test whether nonconscious motives shape daily behavioral decisions, which in turn foster positive emotions that further augment nonconscious motives in an upward spiral dynamic. Studies 1 and 2 use a 3-group experimental design with concurrent behavioral and psychophysiological measures to compare and contrast behavioral decisions that ensue following positive emotions versus physical pleasures, targeting the mediating mechanisms of nonconscious motives (Study 1), and broadened cognition (Study 2). Studies 3 and 4 use a 2 X 2 experimental design to test whether the modifiable resources of positive valuation (Study 3) and oxytocin (Study 4) boost the positive emotion yield of wellness behavior, with attendant benefits for nonconscious motives and subsequent daily behavioral decisions. This program of basic research stands to reshape public health interventions and unlock hidden opportunities to drastically reduce the incidence of cancer and other costly chronic conditions.